Recently, an electroluminescence element has come into use for displays of various electronics and information equipment, and such an electroluminescence element employs a phosphor film. The electroluminescence element generally has a constitution including a lower transparent electrode formed on a glass substrate, a first insulating film formed on the lower transparent electrode, a phosphor film formed on the first insulating film, a second insulating film formed on the phosphor film in the manner of covering the phosphor film with the second insulating film and the first insulating film, and an upper electrode formed on the second insulating film. This constitution is widely known.
The europium-doped barium thioaluminate phosphor film (BaAl2S4:Eu) is known as one of phosphor films used in the electroluminescence element. The europium-doped barium thioaluminate phosphor film is constituted by barium thioaluminate (BaAl2S4) serving as the host component and impurities including europium (Eu) which serve as the emission center. This europium-doped barium thioaluminate phosphor film is formed by first preparing a thin amorphous film by a two-pulse electron-beam evaporation deposition method with the use of a BaS pellet added with an Al2S3 pellet and EuF3 as the vaporization source, and then subjecting to crystallization with heat treatment in an annealing furnace. However, in this method, the phosphor film needs to be treated with heat in a final process and the temperature for this heat treatment has to be as high as 900° C. or above. Accordingly, electrodes and insulating films constituting an electroluminescence element are adversely affected, and thus it has been difficult to obtain completely-crystallized Eu-added barium thioaluminate.
Thereupon, in recent years, there has been developed and proposed a method for producing a europium-doped barium thioaluminate phosphor film by an electron beam (EB) evaporation deposition method with the use of organometallic materials of triethylaluminum (Al(C2H5)3), trimethylaluminum (Al(CH3)3), or triisobutylaluminum (Al(i-C4H9)3), metal barium (Ba), any one of metal europium (Eu), europium chloride (EuCl3), and europium fluoride (EuF3), and hydrogen sulfide (H2S), as the raw materials (see Patent Document 1). In addition, there is no description about the europium-doped barium thioaluminate phosphor film (BaAl2S4:Eu) itself, but it is generally known that a phosphor film in an electroluminescence element is formed by a multi-target sputtering method (see Patent Documents 2 and 3).
[Patent Document 1] Japanese Unexamined Patent Publication No. 2001-297877
[Patent Document 2] Japanese Unexamined Patent Publication No. 2001-118677
[Patent Document 3] Japanese Unexamined Patent Publication No. 8-138867